Flaproo: A Bat-Inspired Flapping Wing Robot

Live animals are uncooperative experimental subjects: they will not repeat a wingbeat on command, and they change their kinematics the moment conditions change. Flaproo is the answer to that problem — a bat-inspired robotic platform that reproduces the wing motion of a frugivorous bat, with anatomically-accurate weight distribution, and lets each degree of freedom be commanded independently.

Three independent degrees of freedom:

• Flapping, driven by a four-bar linkage off a primary motor
• Wing folding, through a timing-belt transmission that rotates the outboard wing relative to the inboard section — enough range for the wings to clap together on the ventral side
• Wing twist, actuated by antagonistically-tensioned Bowden cables that produce a gradual spanwise reduction in pitch angle

With a wingspan of roughly 70 cm and a mean chord of 15 cm, the robot operates at Strouhal numbers typical of animal flight (0.2–0.4), which is what makes its measurements comparable to the live-bird experiments rather than merely analogous. Because the same wingbeat can be repeated indefinitely, direct force and torque measurements become possible in ways that live-animal work cannot support — including in the vortex wake used in the Surfing on Vortices experiments.

The robot was featured by National Geographic.